The present invention relates to tape measures and is more particularly directed to tape measures in which a tape rule is automatically retracted into its casing, but has a lock switch to lock the tape rule in an extended position.
Retractable tape rules are well known and highly useful tools in the carpentry and other trades. Devices have been constructed in the past which permit automatic retraction of the tape rule into a casing, under the influence of a spring-powered retraction unit. A variety of different types of lock members have been proposed for automatic tape rules to lock the tape in a selected extended position and to hold it against retraction under the influence of the spring retraction unit or motor.
It is often difficult to read the tape measure, oweing to lack of available ambient light, for example, during early phases of construction of a building. Because electrical work in a building must often wait until carpentry and other construction is well under way, the inside of a building is often too dark to permit a tradesman to read the measurement on the tape rule. Moreover, it is often necessary for carpenters and other tradesmen to work at night or in closed, unlit surroundings where it is difficult or impossible to read the measurement on the tape rule. A flashlight is often used for this purpose, but the tradesman does not always have a free hand available to shine his flashlight on the rule.
It is an object of the present invention to provide an automatically retractable tape rule in which there is incorporated a reliable and durable mechanism for locking the rule in an extended position and at the same time illuminating the scale on the tape rule.
It is another object of the present invention to provide a retractable tape rule which can be locked with one-hand operation in an extended position, and in the same operation is illuminated to facilitate reading the measurement on the tape rule.
It is a further object of this invention to provide an illuminating arrangement for the tape rule which is built into the casing of the tape rule and which can be switched on and off by the same mechanism that locks and releases the tape rule.
In accordance with an aspect of the present invention, a tape rule having a casing including an opening therein through which an extended tape rule may pass, includes a spring motor or the like for automatically retracting the tape rule into the casing as a coil. The tape rule has indicia thereon, e.g. to indicate inches or centimeters. The tape rule is selectively locked in any desired extended position by actuating a lock member. The same is mounted in the casing for movement between first (lock) and second (unlock) positions. In a favorable embodiment, the lock member has a free end located to engage the tape rule against a portion of the casing in the first position thereby to lock the rule against retraction, and a second position spaced from the rule to permit unimpeded retraction thereof. A slide actuator on the front face of the casing is operatively engaged with the lock member, for example, through a pin and cam slot arrangement, for moving the lock member between its first and second positions.
A lighting device, such as an LED, is disposed in the casing to illuminate the indicia on the tape rule. A power supply, such as a disc power cell, is disposed in the interior of the casing to power the LED, and a switch, completing the circuit including the LED and the power cell, closes and opens in response to movement of the slide actuator to its first and second positions, respectively. As a result, when the tape rule is extended, moving the slide actuator to its lock position both locks the tape rule in its extended position and lights the LED to illuminate the face of the tape rule to facilitate reading it. Moving the slide actuator to its unlocked position releases the tape rule and turns off the LED.